1. Field of the Disclosure
The present disclosure relates to electronic devices and processes, and more particularly to electronic devices including semiconductor regions of different thicknesses over insulating layers and processes of forming the electronic devices.
2. Description of the Related Art
Increased performance of electronic devices is resulting in more complicated structures used in the electronic devices. For integrated circuits, different semiconductor regions of different thicknesses are used in order to meet the designed performance specifications.
One attempt to achieve different thicknesses of semiconductor regions over an insulating layer can include selectively thinning portions of a semiconductor layer. Before selective thinning, the semiconductor layer may have a substantially uniform thickness. One or more masks can be used with one or more etching operations to thin some, but not all of the semiconductor layer. After selective thinning, the uppermost surfaces of the different semiconductor regions may lie at different elevations above a primary surface. The resulting topology can cause problems with lithographic operations (e.g., depth of focus) and polishing operations.
Another attempt to form different thicknesses of semiconductor regions over an insulating layer can include a Separation by Implanted Oxygen (“SIMOX”) process. A semiconductor layer has a substantially uniform thickness over an underlying insulating layer. The semiconductor layer can be selectively implanted with oxygen at one or more regions where a thinner channel region of a transistor structure is desired. SIMOX processes are generally disfavored because they severely damage the one or more portions of the semiconductor layer being implanted, and annealing may not reduce the crystal defect level low enough to be used for high-performance transistors.
Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.